At the time of the gauge-alteration-in-rolling in the cold tandem rolling mill, generally a gauge-alteration-in-rolling amount (a roll gap-alteration amount and a rolling speed-alteration amount) of each of the stands is calculated in advance, during rolling a preceding material, using an estimated rolling load value and an estimated forward slip value, which are obtained by path schedules of the preceding and the succeeding material, a set value of tension between stands, an estimated deformation resistance value, an estimated friction coefficient value, and the like.
On this occasion, there has been proposed a method of, when detectors for measuring the rolling results are available, modifying the gauge-alteration-in-rolling amount using thus obtained rolling results.
For example, there has been known a method of, when a gauge detector is provided on an inlet side of the rolling mill, modifying the roll gap-alteration amount of a first stand using a mother material gauge measured by the inlet side gauge detector. Also, there has been known a method of, when detectors for measuring the rolling load, the tension between the stands, the rolling speed, and the stand outlet side gauge are disposed at a preceding stand, modifying a gauge-alteration-in-rolling amount at a succeeding stand using the rolling results of the preceding stand detected by these detectors.
These methods intend for modifying, using the rolling results, the setting errors of a gauge-alteration-in-rolling amount which results from various wrong estimation carried out for the materials-to-be-rolled.
However, only modifying the gauge-alteration-in-rolling amount using the measured mother material gauge like the former method disables the setting errors resulting from difference in material property of the materials-to-be-rolled, such as a deformation resistance error, to be modified.
Further, according to the latter method of modifying the gauge-alteration-in-rolling amount of the succeeding stand using the rolling results of the preceding stand, calculating the difference in material property of the material-to-be-rolled by some methods using the rolling results, and then modifying the gauge-alteration-in-rolling amount of the succeeding stand using the above calculated material-wise error causes the leading end portion of the succeeding material to be controlled in gauge deviation, which, however, provides the following problems:
For example, when modifying, between the i-th stand and the next (i+1)-th stand, the gauge-alteration-in-rolling amount of the (i+1)-th stand using the results of the i-th stand, the gauge of the leading end portion of the succeeding material exposed at the (i+1)-th stand gets nearer to a desired value as shown by the arrow A in FIG. 7. However, when an AGC (automatic gauge control) of the i-th stand is turned on after the gauge-alteration-in-rolling point B passes through the i-th stand, and hence the gauge deviation, resulting from the wrong setting at the time of the gauge-alteration-in-rolling at the i-th stand, gets nearer to a desired value as shown by the arrow C, the (i+1)-th stand outlet side gauge, which should get nearer to the desired value as shown by the arrow D unless there were no modification, shown by the arrow A, due to the rolling results of the i-th stand, comes off adversely from the leading end portion, as shown by the arrow E, due to the modification shown by the arrow A. This, until the AGC of the (i+1)-th stand is turned on and hence the (i+1)-th stand outlet side gauge returns to the desired value as shown by the arrow F, reversely increases the gauge deviation, which undesirably provides the off gauge.